The detailed mechanism of iron uptake by human leukemic K562 cells were studied. These studies have documented a unique endocytotic pathway in which iron is carried into the cell attached to transferrin via the surface receptor for this serum glycoprotein. An acidic organelle was identified which is likely the site of iron transfer to cytosolic ferritin. At no point in this pathway does transferrin enter lysosomes but, rather, releases its iron and is then is itself released from the cell. The unusual folding properties of ovalbumin were studied and the amino terminus was identified as the functional leader sequence. Currently the glycoproteins of Herpes Simplex Virus are being studied with two major goals: (a) to study intracellular movement of the membrane glycoproteins and (b) to establish clonal cells lines that have integrated and express Herpes membrane glycoproteins in order to study the regulation of metabolism and topology of proteins in a living cell.